Royal Melbourne Hospital has revealed four in 10 of its COVID-19 infected staff were from the Royal Park campus, despite the site only accounting for about 10 per cent of its workforce.
In a new peer-reviewed report published in the Medical Journal of Australia on Monday, the hospital laid out its response in curbing the outbreak.
The journal said it has been the nation's largest institutional outbreak among healthcare workers.
There were 262 Royal Melbourne Hospital staff who caught coronavirus from July 1 to August 31 and more forced into quarantine as close contacts, leading to "high workloads".
The hardest-hit profession was nurses with 179 cases, while the 550-bed campus at Royal Park was the worst-affected site as it recorded 107 infections - making up 40.8 per cent of all staff cases.
The campus closed four wards in August as cases exploded among staff after receiving a large intake of COVID-positive aged care residents.
Although ventilation systems were found to satisfy requirements, RMH decided to move 15 patients to other health services and transfer the remaining 45 to single rooms in more modern wards.
"We hypothesised that large numbers of patients in confined spaces may have created a high density of droplets, aerosols and environmental contamination," wrote the authors, led by infectious diseases physician Kirsty Buising.
"This triggered a detailed assessment of ward physical layout, including the possible role of patient placement and air circulation.
"We elected to use single rooms wherever possible and to physically space infected patients by closing beds on the ward."
N95 masks were also handed out to staff working in areas with large concentrations of confirmed or suspected COVID-19 patients, over and above state and federal guidelines at the time.
Other recommendations for future healthcare worker outbreaks included a rapid staff testing program and improving access to employee support initiatives.
ROYAL MELBOURNE HOSPITAL STAFF CASES ACROSS JULY AND AUGUST
* 262 confirmed cases
* 205 women (78.2 per cent), 57 men (21.8 per cent)
* 32.7 median age at diagnosis
* 179 nurses
* 38 support staff (food services and environmental services)
* 21 doctors
* Nine allied health practitioners
* Six administrative staff
* Four students
* Four security staff
* One laboratory staff member
* 107 cases from Royal Park Campus (rehabilitation, geriatric rehabilitation)
* 57 from hot wards (COVID-19 wards, emergency departments and intensive care units)
* 20 from cold wards with known outbreaks (three wards)
* Seven from cold wards with no outbreak (one or two unlinked cases, six wards)
* Eight at mental health wards
* 31 not ward-based (non-clinical cases)
* 32 unknown (no campus or ward across both campuses).